1. Field of the Invention
The present invention generally relates to semiconductor chip manufacture and more particularly to formation of lateral and vertical isolation structures.
2. Background Description SIMOX (Separation by IMplantation of OXygen) uses a high-dose oxygen implant to form a buried SiO.sub.2 layer. As described by Leray et al. ("An Overview of Buried Oxides on Silicon: New Processes and Radiation Effects", J. Phys. III France 6 (1996) 1625-1646.), an insulating layer is obtained underneath the silicon surface by implantation of oxygen ions in a silicon wafer. The energy of the oxygen ions directly determines the range and profile of the implanted layer. Ion energy and oxygen fluence determine the thickness of buried oxide and top silicon layer over buried oxide.